Water-miscible metal working fluids with reduced aerosol inhalation toxicity

ABSTRACT

The present invention provides a process for producing a water-miscible metalworking fluid involving combining about 90 wt. % to about 5 wt. %, based on the weight of the fluid, of water and one or more additives chosen from plasticizers, chelating agents, biocides, surfactants, dispersants, dyes, odorants, extreme pressure agents, anti-oxidants and corrosion inhibitors with about 10 wt. % to about 95 wt. %, based on the weight of the fluid, of a polyether polyol produced by mixing an active hydrogen compound with a double metal cyanide (DMC) catalyst in a reactor vessel, charging to the reactor vessel a mixture containing two or more alkylene oxides to activate the catalyst, and continuously feeding one or more alkylene oxides to produce the polyether polyol, wherein a 1% solution in water of the polyether polyol has a cloud point of from greater than about 32° C. to less than about 53° C., the polyether polyol has a number average equivalent weight of from greater than about 1,600 Da to about 10,000 Da, and a four-hour aerosol inhalation exposure to the polyether polyol has a LC 50  of greater than about 5 mg/L. The water-miscible metalworking fluid produced by the inventive process may find use in cooling and/or lubricating metal surfaces during one or more of grinding, cutting, boring, drilling and turning of metal parts.

The present application is a continuation-in-part of, and claims thebenefit of prior application Ser. No. 11/332,071, filed Jan. 13, 2006.

FIELD OF THE INVENTION

The present invention relates, in general to functional fluids, and morespecifically to synthetic, water-miscible metalworking fluids (MWFs)which provide effective cooling and lubrication of metal surfaces athigh speeds of operation in the grinding, cutting, boring, drilling,and/or turning of metal parts, while also reducing aerosol inhalationtoxicity.

BACKGROUND OF THE INVENTION

Metalworking processes mechanically shape and work metallic articles orwork pieces. Metalworking fluids (or metal removal fluids) are oftenused for the lubrication of metal cutting and forming tools. Thesefluids also provide cooling for the tool, facilitate the removal of cutchips or fragments from the tool-work piece interface, and help toprovide an acceptable post-machining finished surface. Becausemetalworking fluids have the effect of reducing the cutting forcesexerted on a tool and work piece, such fluids can significantly extendthe life of the tool.

However, one of the problems associated with the use of metalworkingfluids results from the nature of the metalworking operations, i.e., awork piece rotates at a relatively high speed and both the work pieceand a metalworking tool are lubricated by a metalworking fluid. Undersuch conditions, the metalworking fluid is frequently thrown from thesurface of the metal in the form of droplets. Oftentimes, these dropletsare small enough to be classified as a mist which may pose a potentialinhalation risk to the metal worker.

In 1993, the United Automobile Aerospace and Agricultural ImplementWorkers of America (UAW) filed a petition requesting that the U.S. Dept.of Labor's Occupational Safety & Health Administration (OSHA) takeregulatory action to protect workers from the potential risks of cancerand respiratory illness arising from exposure to metalworking fluids(MWFs). In response, OSHA convened the Metalworking Fluids StandardAdvisory Committee in 1997 to “. . . advise the agency on appropriateactions to protect workers from the hazards associated with occupationalexposure to MWFs”.

In 2001, OSHA issued the publication, “Metalworking Fluids: Safety andHealth Best Practices Manual” to provide guidelines for reducingemployee exposure to MWFs and to provide information on the healthhazards of occupational exposure. This manual recommends that, “. . .the MWFs selected should be as non-irritating and non-sensitizing aspossible. . . . Acute toxicity characteristics of metalworking fluidscan be evaluated using information contained in ASTM Standard E-1302-00,Standard Guide for Acute animal Toxicity Testing of Water-MiscibleMetalworking Fluids”.

To date, most industry efforts have focused on reducing worker exposurethrough engineering modifications or through the use of anti-mistingaids. One such solution is exemplified by U.S. Pat. No. 6,344,517,issued to Quinn et al., which describes water-soluble orwater-dispersible polymeric acrylate derivatives as additives for mistreduction and shear stability in metalworking formulations.

Although such suspected cancer-causing agents as alkali metal nitrites,chromates, and para-tert-butylbenzoic acid have been removed fromwater-based metalworking fluids, there still may be concerns regardingpossible respiratory problems from the inhalation of aerosols generatedfrom butanol-started polyether polyols that are the primary constituentsof many synthetic, water-miscible metalworking fluids.

In a report by the European Centre for Ecotoxicology and Toxicology ofChemicals (ECETOC) entitled, “Technical Report No. 55-Pulmonary Toxicityof Polyalkylene Glycols” published in 1997, certain 50:50 ethyleneoxide-propylene oxide (EO-PO) random copolymers initiated with butanolwere identified as being toxic in aerosol inhalation studies withanimals. No butanol-initiated EO-PO copolymers above a 1,000 equivalentweight met the limit test of an LC₅₀ greater than 5 mg/L as described inASTM Standard E-1302-00. For inhalation experiments, the concentrationof the chemical in air that kills 50% of the test animals in a giventime (typically four hours) is termed the LC₅₀ value. As a general rule,the smaller the LC₅₀ value, the higher the toxicity. The opposite alsoholds true, i.e., the larger the LC₅₀ value, the lower the toxicity.

Typically, water-miscible polyether polyols useful in metalworkingfluids have been prepared by semi-batch processes involving thebase-catalyzed anionic polymerization of alkylene oxides. As thoseskilled in the art are aware, in such processes an active hydrogencompound is charged to a reactor along with a basic catalyst, such assodium or potassium hydroxide, the mixture is dehydrated, and analkylene oxide or mixture of alkylene oxides is added to produce thepolyether. Usually, these polyols are random copolymers prepared frombutanol, ethylene oxide (EO), and propylene oxide (PO) and have beenmarketed under such trade names as the PLURASAFE WS fluid series (BASFCorp.) and the UCON HB fluid series (Dow Chemical Co.).

One solution to the problem of aerosol toxicity for base-catalyzedpolyols is disclosed by Pollmann et al., in U.S. Published PatentApplication 2001/0031855 A1, where ethylene oxide-propylene oxidecopolymers of higher functionality polyether polyols containing centralbranch points are shown to have LC₅₀ values greater than about 5 mg/L.However, the branched polyether polyols of Pollmann et al. aresufficiently different in performance from current butanol-startedcompounds that reformulation of metalworking additive packages would berequired and thus their ultimate performance may not be comparable.

As those skilled in the art are aware, double metal cyanide (DMC)catalysts have been used to prepare polyether polyols. These catalysts,which have a low tendency to promote isomerization of propylene oxide toallylic unsaturates and have faster rates of reaction, are prepared bythe reaction of hexacyanometallate salts with transition metal salts inthe presence of suitable organic ligands.

An example of DMC catalyst utilization for the preparation of randomcopolymers of ethylene and propylene oxide can be found in EP 0,992,523B1, issued to Miller et al., which describes a process for theactivation or initiation of the catalyst with 100% propylene oxide priorto feeding a mixture of ethylene oxide and propylene oxide to make amonofunctional polyether for use in silicone surfactant production.However, Miller et al., are silent as to any risks associated withaerosol or mist exposure to their polyethers.

Clement et al., in U.S. Pat. No. 6,642,423, teach that DMC catalysts areuseful for the preparation of ethoxylates from starters which aresensitive to conventional basic or Lewis acid type catalysts. However,polyether polyols prepared in accordance with processes used in Clementet al., contain a pure block of ethylene oxide adjacent to the initiatormolecule. Conversely, U.S. Published Patent Application 2005/0181967 A1in the name of Ruland et al., discloses alkoxylates prepared from C₁₀alkanols in the presence of DMC catalysts where a pure propyleneoxy,buteneoxy, or penteneoxy block is attached to the initiator.

Ruland et al., in U.S. Published Patent Application 2005/0215452 A1,also teach the use of DMC catalysts to prepare C₁₀ alcohol-initiatedpolyether polyols with block or random copolymer structures but aresilent with respect to the benefits of catalyst activation with analkylene oxide mixture for reduced aerosol inhalation toxicity.

Polyether polyols useful as foam suppressants can be made using DMCcatalysts as described in U.S. Pat. No. 7,001,634, issued to Browne.However, those random copolymers are marginally water soluble atslightly elevated temperatures with cloud points for 1% aqueoussolutions being less than 30° C. Browne is also silent regardingpotential risks associated with aerosol or mist exposure to his foamsuppressants in metalworking applications.

Sherman et al., in U.S. Published Patent Application 2005/0256014 A1,teach that EO-PO copolymer monols and diols with unsaturation levelsbelow 0.01 meq/g exhibit low pulmonary toxicity. However, it iswell-known by those skilled in the art that some of the lower equivalentweight base-catalyzed commercial products mentioned in the previouslyreferenced ECETOC Technical Report 55 have low levels of unsaturationand low pulmonary toxicity. For example, Table 1 of the Reportillustrates that typical values for unsaturation of 2,000 equivalentweight butanol-started monols are less than about one percent, whichcorresponds to less than about 0.005 meq/g of unsaturation. Sherman etal. also disclose the parallel addition of a monol or diol initiatoralong with the alkylene oxides. However, there still exists a desire toprovide a detailed method for the production of higher equivalent weightpolyols with acute aerosol inhalation LC₅₀ values greater than about 5mg/L for use in industrial applications where there is a potential forthe production of mists or aerosols.

Therefore, an improved process is needed for the production ofwater-miscible metalworking fluids that are less toxic with respect toaerosol inhalation exposure than are currently available commercialproducts. More importantly, a process for the production of polyetherpolyols for metalworking fluids that meet or exceed the limit test of anLC₅₀ greater than about 5 mg/L, as defined in ASTM Standard E-1302-00,at equivalent weights greater than about 1,600 Da would be verydesirable.

SUMMARY OF THE INVENTION

The present invention provides such a process for producing awater-miscible metalworking. fluid involving combining about 90 wt. % toabout 5 wt. %, based on the weight of the fluid, of water and one ormore additives chosen from plasticizers, chelating agents, biocides,surfactants, dispersants, dyes, odorants, extreme pressure agents,anti-oxidants and corrosion inhibitors with about 10 wt. % to about 95wt. %, based on the weight of the fluid, of a polyether polyol producedby mixing an active hydrogen compound with a double metal cyanide (DMC)catalyst in a reactor vessel, charging to the reactor vessel a mixturecontaining two or more alkylene oxides to activate the catalyst, andcontinuously feeding one-or more alkylene oxides-to produce thepolyether polyol, wherein a 1% solution in water of the polyether polyolhas a cloud point of from greater than about 32° C. to less than about53° C., the polyether polyol has a number average equivalent weight offrom greater than about 1,600 Da to about 10,000 Da, and a four-houraerosol inhalation exposure to the polyether polyol has a LC₅₀ ofgreater than about 5 mg/L.

These and other advantages and benefits of the present invention will beapparent from the Detailed Description of the Invention herein below.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described for purposes of illustrationand not limitation. Except in the operating examples, or where otherwiseindicated, all numbers expressing quantities, percentages, hydroxylnumbers, functionalities and so forth in the specification are to beunderstood as being modified in all instances by the term“about.”Equivalent weights and molecular weights given herein in Daltons (Da)are number average equivalent weights and number average molecularweights respectively, unless indicated otherwise.

The present invention provides a process for producing a water-misciblemetalworking fluid involving combining 90 wt. % to 5 wt. %, based on theweight of the fluid, of water and one or more additives chosen fromplasticizers, chelating agents, biocides, surfactants, dispersants,dyes, odorants, extreme pressure agents, anti-oxidants and corrosioninhibitors with 10 wt. % to 95 wt. %, based on the weight of the fluid,of a polyether polyol produced by mixing an active hydrogen compoundwith a double metal cyanide (DMC) catalyst in a reactor vessel, chargingto the reactor vessel a mixture containing two or more alkylene oxidesto activate the catalyst, and continuously feeding one or more alkyleneoxides to produce the polyether polyol, wherein a 1% solution in waterof the polyether polyol has a cloud point of from greater than 32° C. toless than 53° C., the polyether polyol has a number average equivalentweight of greater than 1,600 Da to 10,000 Da, and a four-hour aerosolinhalation exposure to the polyether polyol has a LC₅₀ of greater than 5mg/L.

The present invention further provides a process for producing awater-miscible metalworking fluid involving combining 90 wt. % to 5 wt.%, based on the weight of the fluid, of water and one or more additiveschosen from plasticizers, chelating agents, biocides, surfactants,dispersants, dyes, odorants, extreme pressure agents, anti-oxidants andcorrosion inhibitors with 10 wt. % to 95 wt. %, based on the weight ofthe fluid, of a polyether polyol produced by mixing with a double metalcyanide (DMC) catalyst in a reactor vessel an initiator chosen from oneor more of a polyol from a prior preparation (heel) having an equivalentweight greater than 300 Da, a lower molecular weight active hydrogencompound that does not deactivate the DMC catalyst and an inert solvent,charging to the reactor vessel a mixture containing two or more alkyleneoxides to activate the catalyst, and continuously feeding one or morealkylene oxides and one or more starters to produce the polyetherpolyol, wherein a 1% solution in water of the polyether polyol has acloud point of from greater than 32° C. to less than 53° C., thepolyether polyol has a number average equivalent weight of greater than1,600 Da to 10,000 Da, and a four-hour aerosol inhalation exposure tothe polyether polyol has a LC₅₀ of greater than 5 mg/L.

The inventors herein have unexpectedly discovered that double metalcyanide (DMC) catalysts can be used to prepare random copolymers ofethylene and propylene oxide that exhibit reduced toxicity to animals asmeasured by acute aerosol inhalation toxicity testing. Morespecifically, the inventors have discovered a process for the activationof DMC catalysts with a mixture of alkylene oxides in which thepolymerization product has a number average equivalent weight of fromgreater than 1,600 Da to 10,000 Da, more preferably 1,600 to 6,000, iswater-miscible with a cloud point of from greater than 32° C. to lessthan 53° C., and has a LC₅₀ greater than 5 mg/L for a four-hour aerosolexposure.

As used herein, the term “water-miscible metalworking fluid” means aliquid containing water, additives that help “wet” the part and otheradditives to improve performance and a polyether polyol. The polyetherpolyol makes up from 10 to 95 wt. %, more preferably from 40 to 90 wt. %of the water-miscible metalworking fluid produced by the inventiveprocess. Water makes up from 90 to 5 wt. % more preferably from 60 to 10wt. %, with the remainder of the water-miscible metalworking fluid beingone or more additives. Suitable additives include, but are not limitedto, plasticizers, chelating agents, surfactants, biocides, dispersants,dyes, and odorants, extreme pressure agents, anti-oxidants, andcorrosion inhibitors to improve performance and increase fluid life.

Suitable examples of methods for the preparation of DMC catalysts andthe use thereof in the manufacture of polyether polyols can be found inU.S. Pat. Nos. 3,278,457, 3,404,109, 3,941,849 and 5,158,922, 5,482,908,5,783,513, 6,613,714, 6,855,658, the entire contents of which areincorporated herein by reference thereto.

As those skilled in the art are aware, DMC catalysts are made by thereaction of hexacyanometallate salts with transition metal salts in thepresence of suitable complexing organic ligands and optionally withfunctionalized polymers or other processing aids to produce a compoundwith the formula given below:M¹ _(x)[M²(CN)₆]_(y).zM¹(X)_(q).Lwherein,

-   M¹ represents a metal selected from the group consisting of Zn⁺²,    Fe⁺², Ni⁺², Mn⁺², Co⁺², Sn⁺², Pb⁺², Fe⁺³, Mo⁺⁴, Mo⁺⁶, Al⁺³, V⁺⁴,    V⁺⁵, Sr⁺², W⁺⁴, W⁺⁶, Cu⁺² and Cr⁺³;-   M² represents a metal selected from the group consisting of Fe⁺²,    Fe⁺³, Co⁺², Co⁺³, Cr⁺², Cr⁺³, Mn⁺², Mn⁺³, Ir⁺³, Ni⁺², Rh⁺³, Ru⁺²,    V⁺⁴ and V⁺⁵,-   X represents an anion selected from the group consisting of halide,    hydroxide, sulfate, carbonate, cyanide, thiocyanide, carboxylate, or    nitrate;-   L represents an organic ligand; and x, y, and q are chosen to    maintain electroneutrality.

Particularly preferred for use in the present invention are those zinchexacyanocobaltate catalysts prepared by the methods described in U.S.Pat. No. 5,482,908, the entire contents of which are incorporated hereinby reference thereto. The DMC catalyst may also be bound to a support asdescribed in U.S. Pat. No. 6,362,126.

Any monofunctional or polyfunctional active hydrogen compound may beoxyalkylated in the process of the invention. Suitable monofunctionalinitiators include, but are not limited to, methanol, ethanol, propanol,butanol, pentanol, phenols, C₆-C₃₆ branched or linear alcohols, andmonofunctional ethers of polypropylene glycols, polyethylene glycols,polybutylene glycols, and polyoxyalkylene glycol copolymers.Polyfunctional initiators include, but are not limited to, water,ethylene glycol, propylene glycol, diethylene glycol, dipropyleneglycol, triethylene glycol, tripropylene glycol, propanediol, glycerine,trimethylolpropane, butanediol isomers, pentaerythritol, polypropyleneglycols, polyethylene glycols, polybutylene glycols, and polyoxyalkyleneglycol copolymers. Butanol is particularly preferred as the activehydrogen compound.

The alkylene oxides useful in the present invention include, but are notlimited to, ethylene oxide, propylene oxide, 1,2- and 2,3-butyleneoxide, isobutylene oxide, epichlorohydrin, cyclohexene oxide, styreneoxide, and the higher alkylene oxides such as the C₅-C₃₀ α-alkyleneoxides. Other polymerizable monomers may be used as well, e.g.anhydrides and other monomers as disclosed in U.S. Pat. Nos. 3,404,109,3,538,043 and 5,145,883, the contents of which are herein incorporatedin their entireties by reference thereto. A mixture of ethylene oxideand propylene oxide is particularly preferred wherein the amount ofethylene oxide is preferably less than 50% of the mixture.

The process of the present invention may be semi-batch or continuous asdescribed in U.S. Pat. No. 5,777,177, the entire contents of which areincorporated herein by reference thereto. In the inventive variation ofthe continuous process described in the '177 Patent, the starter orinitiator is preferably a monofunctional or polyfunctional activehydrogen compound with an average equivalent weight less than 300 Da,while the material charged initially to the reaction vessel may be oneor more of a polyol from a prior preparation (heel) with an equivalentweight greater than 300 Da, a lower molecular weight active hydrogencompound that does not deactivate the DMC catalyst, and an inertsolvent.

The water-miscible metalworking fluids prepared by the process of thepresent invention may preferably be used to cool and/or lubricate metalsurfaces during the grinding, cutting, boring, drilling and/or turningof metal parts.

EXAMPLES

The present invention is further illustrated, but is not to be limited,by the following examples. All quantities given in “parts” and“percents” are understood to be by weight, unless otherwise indicated.

Example 1

This example employed a product-to-product process together withcontinuous addition of starter (CAOS), in which a heel of product(prepared from butanol and propylene oxide/ethylene oxide to a hydroxylnumber of about 35 mg KOH/g via a CAOS process) was added to the reactorat the beginning of the batch, a mixture of ethylene oxide and propyleneoxide was added to activate the catalyst, and an initiator or starterwas fed continuously to the reactor simultaneously with the alkyleneoxide or oxides after activation. Double metal cyanide (DMC) catalystprepared according to U.S. Pat. No. 5,482,908 was used in all examples.A heel of 2,500 g of product was added to a 20 kg reactor along with DMCcatalyst (0.87 g). The mixture was dehydrated with vacuum and nitrogenfor 30 minutes at 130° C. The catalyst was activated with 125 g of mixedoxide (50 wt. % propylene oxide, 50 wt. % ethylene oxide) fed at 130° C.After the pressure drop in the reactor confirmed catalyst initiation,propylene oxide (8,306 g), ethylene oxide (8,306 g), and n-butanol (763g) were added to. the reactor simultaneously over a six-hour period at130° C. to produce a polyether with a hydroxyl number of about 34 mgKOH/g. This product had an number average equivalent weight of 1,716g/mol, a viscosity of 810 SUS at 37.8° C., a cloud point (1% in water)of 52° C., and an LC₅₀ concentration of >5.83 mg/L for a four-houraerosol exposure.

Example 2

The procedure described above in Example 1 was repeated, except theethylene oxide/propylene oxide ratio was 35/65, and the amount ofn-butanol fed was reduced to produce a polyether with a hydroxyl numberof about 17 mg KOH/g. The resulting product had a number averageequivalent weight of 3,187 g/mol, a viscosity of 2,060 SUS at 37.8° C.,a cloud point (1% in water) of 40° C., and an LC₅₀ concentrationof >5.38 mg/L for a four-hour aerosol exposure.

Example 3

A semi-batch process, in which alkylene oxides are added to an initiatorwithout the presence of a continuous starter feed was used. The reactorwas charged with 5,426 g of product similar to that described in Ex. 1above together with DMC catalyst (0.9 g). The mixture was dehydratedwith vacuum and nitrogen for 30 minutes at 130° C. The catalyst wasactivated with 271 g of mixed oxide (50 wt. % propylene oxide, 50 wt. %ethylene oxide) fed at 130° C. After the pressure drop in the reactorconfirmed catalyst initiation, propylene oxide (6,204 g) and ethyleneoxide (6,204 g) were added to the reactor simultaneously over afive-hour period to produce a polyether with a hydroxyl number of about10 mg KOH/g. This product had an number average equivalent weight of5,968 g/mol, a viscosity of 5,340 SUS at 37.8° C., a cloud point (1% inwater) of 56° C., and an LC₅₀ concentration <5.9 mg/L for a four-houraerosol exposure.

As can be appreciated by reference to Table I below, butanol-initiatedrandom copolymers of EO and PO with higher equivalent weights that meetthe limit value of 5 mg/L can be produced by the inventive process.Although, the present invention allows for the formulation and selectionof less toxic polyether polyol for metalworking fluids (MWFs) based onthe inhalation test protocols referenced in the OSHA “MetalworkingFluids: Safety and Health Best Practices Manual”, the inventors hereincaution that such polyols should be evaluated for aerosol inhalationtoxicity on an individual basis.

Example 4

The procedure described above in Example 2 was repeated, except theethylene oxide/propylene oxide ratio was 50/50. The resulting producthad a weight average equivalent weight of 3,645 g/mol, a viscosity of2,298 SUS at 37.8° C., a cloud point (1% in water) of 53° C., and anLC₅₀ concentration of <5 mg/L for a four-hour aerosol exposure.

Example 5

The procedure described above in Example 3 was repeated, except theethylene oxide/propylene oxide ratio was 35/65. The resulting producthad a weight average equivalent weight of 5250 g/mol, a viscosity of4762 SUS at 37.8° C., a cloud point (1% in water) of 37.7° C., and anLC₅₀ concentration of >5 mg/L for a four-hour aerosol exposure. TABLE IViscosity Cloud point LC₅₀ (SUS at (1% in four hour¹ Ex. No. EO/POEquiv. Wt. 38° C.) water) (mg/L) 1 50/50 1,716 810 52 >5.83 2 35/653,187 2,060 40 >5.38 3 50/50 5,968 5,340 56 <5.90 4 50/50 3573 2298 53<5.4 5 35/65 5447 4762 37.7 >5.1¹Four-hour, nose-only, exposure using female and male Sprague-Dawleyrats.

TABLE II LC₅₀ Viscosity Cloud point four Commercial (SUS at (1% in hour²Product³ EO/PO Equiv. Wt. 38° C.) water) (mg/L) 50-HB-660 50/50 1,590660 55 4.5 50-HB-2000 50/50 2,620 2,000 52 0.35 50-HB-5100 50/50 3,9305,100 50 0.10²Commercial product acute inhalation data from Technical Report No. 55by ECETOC, 1997.³Physical property data for commercial products from UCON Fluids andLubricants brochure by Dow Chemical Company.

The foregoing examples of the present invention are offered for thepurpose of illustration and not limitation. It will be apparent to thoseskilled in the art that the embodiments described herein may be modifiedor revised in various ways without departing from the spirit and scopeof the invention. The scope of the invention is to be measured by theappended claims.

1. A process for producing a water-miscible metalworking fluidcomprising combining: about 90 wt. % to about 5 wt. %, based on theweight of the fluid, of water; and one or more additives chosen fromplasticizers, chelating agents, biocides, surfactants, dispersants,dyes, odorants, extreme pressure agents, anti-oxidants and corrosioninhibitors; with about 10 wt. % to about 95 wt. %, based on the weightof the fluid of a polyether polyol produced by mixing an active hydrogencompound with a double metal cyanide (DMC) catalyst in a reactor vessel,charging to the reactor vessel a mixture containing two or more alkyleneoxides to activate the catalyst, and continuously feeding one or morealkylene oxides to produce the polyether polyol, wherein a 1% solutionin water of the polyether polyol has a cloud point of from greater thanabout 32° C. to less than about 53° C., the polyether polyol has anumber average equivalent weight of from greater than about 1,600 Da toabout 10,000 Da, and a four-hour aerosol inhalation exposure to thepolyether polyol has a LC₅₀ of greater than about 5 mg/L.
 2. The processaccording to claim 1, wherein the active hydrogen compound is chosenfrom methanol, ethanol, propanol, butanol, pentanol, phenols, C₆-C₃₆branched or linear alcohols, monofunctional ethers of polypropyleneglycols, polyethylene glycols, polybutylene glycols, polyoxyalkyleneglycol copolymers, water, ethylene glycol, propylene glycol, diethyleneglycol, dipropylene glycol, triethylene glycol, tripropylene glycol,propanediol, glycerine, trimethylolpropane, butanediol isomers,pentaerythritol, polypropylene glycols, polyethylene glycols,polybutylene glycols and polyoxyalkylene glycol copolymers.
 3. Theprocess according to claim 1, wherein the active hydrogen compound isbutanol.
 4. The process according to claim 1, wherein the DMC catalystis a zinc hexacyanocobaltate.
 5. The process according to claim 1,wherein the mixture contains two or more alkylene oxides chosen fromethylene oxide, propylene oxide, 1,2- and and 2,3-butylene oxide,isobutylene oxide, epichlorohydrin, cyclohexene oxide, styrene oxide andC₅-C₃₀ α-alkylene oxides.
 6. The process according to claim 1, whereinthe continuous feeding is of one or more alkylene oxides chosen fromethylene oxide, propylene oxide, 1,2- and 2,3-butylene oxide,isobutylene oxide, epichlorohydrin, cyclohexene oxide, styrene oxide andC₅-C₃₀ α-alkylene oxides.
 7. The process according to claim 1, whereinthe water-miscible metalworking fluid comprises from about 40 wt. % toabout 90 wt. %, based on the weight of the fluid, of the polyetherpolyol and from about 60 wt. % to about 10 wt. %, based on the weight ofthe fluid, of water.
 8. The process according to claim 1, wherein thepolyether polyol has a number average equivalent weight of from about1,600 Da to about 6,000 Da.
 9. The water-miscible metalworking fluidproduced by the process according to claim
 1. 10. A process forproducing a water-miscible metalworking fluid comprising combining:about 90 wt. % to about 5 wt. %, based on the weight of the fluid, ofwater; and one or more additives chosen from plasticizers, chelatingagents, biocides, surfactants, dispersants, dyes, odorants, extremepressure agents, anti-oxidants and corrosion inhibitors; with about 10wt. % to about 95 wt. %, based on the weight of the fluid, of apolyether polyol produced by mixing with a double metal cyanide (DMC)catalyst in a reactor vessel an initiator chosen from one or more of apolyol from a prior preparation (heel) having an equivalent weightgreater than about 300 Da, a lower molecular weight active hydrogencompound that does not deactivate the DMC catalyst and an inert solvent,charging to the reactor vessel a mixture containing two or more alkyleneoxides to activate the catalyst, and continuously feeding one or morealkylene oxides and one or more starters to produce the polyetherpolyol, wherein a 1% solution in water of the polyether polyol has acloud point of from greater than about 32° C. to less than about 53° C.,polyether polyol has a number average equivalent weight of from greaterthan about 1,600 Da to about 10,000 Da, and a four-hour aerosolinhalation exposure to the polyether polyol has a LC₅₀ of greater thanabout 5 mg/L.
 11. The process according to claim 10, wherein theinitiator is a polyol from a prior preparation (heel) having anequivalent weight greater than about 300 Da.
 12. The process accordingto claim 10, wherein the initiator is a lower molecular weight activehydrogen compound that does not deactivate the DMC catalyst.
 13. Theprocess according to claim 10, wherein the initiator is an inertsolvent.
 14. The process according to claim 10, wherein the DMC catalystis a zinc hexacyanocobaltate.
 15. The process according to claim 10,wherein the mixture contains two or more-alkylene oxides chosen fromethylene oxide, propylene oxide, 1,2- and 2,3-butylene oxide,isobutylene oxide, epichlorohydrin, cyclohexene oxide, styrene oxide andC₅ -C₃₀ α-alkylene oxides.
 16. The process according to claim 10,wherein the continuous feeding is of one or more alkylene oxides chosenfrom ethylene oxide, propylene oxide, 1,2- and 2,3-butylene oxide,isobutylene oxide, epichlorohydrin, cyclohexene oxide, styrene oxide andC₅-C₃₀ α-alkylene oxides.
 17. The process according to claim 10, whereinthe starter is chosen from methanol, ethanol, propanol, butanol,pentanol, phenols, C₆-C₃₆ branched or linear alcohols, monofunctionalethers of polypropylene glycols, polyethylene glycols, polybutyleneglycols, polyoxyalkylene glycol copolymers, water, ethylene glycol,propylene glycol, diethylene glycol, dipropylene glycol, triethyleneglycol, tripropylene glycol, propanediol, glycerine, trimethylolpropane,butanediol isomers, polypropylene glycols, polyethylene glycols,polybutylene glycols and polyoxyalkylene glycol copolymers.
 18. Theprocess according to claim 10, wherein the starter is butanol.
 19. Theprocess according to claim 10, wherein the water-miscible metalworkingfluid comprises from about 40 wt. % to about 90 wt. %, based on theweight of the fluid, of the polyether polyol and from about 60 wt. % toabout 10 wt. %, based on the weight of the fluid, of water.
 20. Thewater-miscible metalworking fluid produced by the process according toclaim 10.